Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $85.82   10.284%   $94.6457   $94.65   $94.65   $94.60  
  Purchase #2 $68.33   8.386%   $74.0602   $74.06   $74.05   $74.10  
  Purchase #3 $168.75   4.526%   $176.3876   $176.39   $176.40   $176.40  
  Purchase #4 $181.91   8.156%   $196.7466   $196.75   $196.75   $196.70  
  Purchase #5 $5.50   10.143%   $6.0579   $6.06   $6.05   $6.10  
  Purchase #6 $203.52   5.784%   $215.2916   $215.29   $215.30   $215.30  
  Purchase #7 $192.80   9.584%   $211.278   $211.28   $211.30   $211.30  
  7 purchase totals = $906.63       $974.4676   $974.48   $974.50   $974.50